In general, a phase-change memory (random access memory: RAM, parameter-RAM: P-RAM) device is the next generation memory semiconductor judging a phase change of a specific material and storing data. Such a phase-change memory device uses crystal states of a phase-change material, such as a calcogenide compound (Ge—Sb—Te: GST) containing germanium (Ge), antimony (Sb) and tellurium (Te). The phase-change memory device stores data in such a manner that it detects signal 1 in the case of a phase-change material present in a crystalline state, and detects signal 0 in the case of a phase-change material present in an amorphous state. Thus, the phase-change memory device has advantages of both flash memory, in which stored data are not deleted even if its power source is interrupted, and dynamic random access memory (DRAM), in which stored data are extinguished upon interruption of its power source but a high processing rate is realized. However, as integration density of a semiconductor device increases, it becomes very difficult to fabricate an ultrafine phase-change memory, particularly a micropatterned phase-change memory device in a large scale due to a unique limitation in photolithography technology for forming patterns and holes.
In other words, Joule heating occurs at an interface between a bottom electrode of phase-change memory and a phase-change material, and an extent of RESET current increases in proportion to the magnitude of interface area. In addition, as RESET current increases, power consumption of a device increases accordingly (P=I^2R). Therefore, it is required to reduce the area of an electrode, particularly a bottom electrode, systematically to reduce RESET current. In this context, there is a problem in that critical dimension (CD) decreases as a device integration degree increases and thus photolithography processes reach the technological limit, while processes of reducing CD of a bottom electrode contact (BEC) also reach the technological limit. In other words, since the area between a phase-change material and an electrode is reduced significantly due to upsizing and high integration of memory devices, it is very difficult to control such a fine contact area between the phase-change layer and the electrode. Therefore, there is an imminent need for technology controlling the threshold value of RESET current, which is the minimum current extent capable of changing crystal states of a phase-change layer, by adjusting area between the phase-change layer and the electrode.